Investigators were reviewing surveillance video of three kids seen running away near the historic Lower East Side synagogue that caught on fire Sunday.

The cause of Sunday night’s fire remained under investigation Monday, as the faint smell of smoke still lingered in the air around what remained of the unoccupied Beth Hamedrash Hagodol synagogue at 60 Norfolk St.

The 3-alarm blaze broke out at about 7 p.m. and the flames ripped through the building, built in 1850 and landmarked in 1967. It took nearly two hours to bring them under control.

Rabbi Mendel Greenbaum, who has headed the synagogue for about 30 years, said all Torahs, religious scrolls and artifacts were safe and not inside the building at the time of the fire. They have been stored in Brooklyn, he said, since the building shut its doors. The building closed in 2007 because membership had dwindled, the rabbi said.

“Everybody’s in shock,” said Greenbaum, whose father-in-law was rabbi for many decades before him.

“I had to hold on not to collapse,” he added, about hearing the news of the fire. “For us, besides a community tragedy, it’s a personal family tragedy as well.”

The congregation did not have the money to repair damages caused by an earlier fire and submitted an application to the Landmark Preservation Commission in 2013 to demolish the building, according to the Tree of Life Heritage Foundation, which had been working to save the synagogue.

Recently, however, Greenbaum said the congregation had reconsidered and was in the “final steps” of meeting with the Department of Buildings and the New York City Landmarks Preservation Commission, adding: “through intervening from some people, good friends, we changed our mind and we were all out to save the building, to save the landmark.”

Beth Hamedrash Hagodol had been the oldest Orthodox congregation of Russian Jews in the United States, according to the Lower East Side Jewish Conservancy, and had used the building on Norfolk Street since 1885. Before it was a synagogue, the building functioned as a church.

“It was a very chilling thing for all of us to hear about,” said Amy Stein-Milford, the deputy director of the Museum at Eldridge Street. “This was an important historic and spiritual landmark of the Lower East Side, and one that we felt had a particular resonance for us.”

The synagogue has seen its share of noted rabbis, including Rabbi Jacob Joseph, who became the first and only chief rabbi of New York City, according to the Conservancy. Joseph led the congregation from 1888 to 1902, during what Rabbi Adam Mintz, an adjunct associate professor of Jewish studies at City College, characterized as the “heyday” for the synagogue.

“This was an important moment — an unfortunate moment — but an important moment for the Jews in New York,” he said about Sunday’s fire. “Its tragic that we’re losing that history. The synagogue, the history of Judaism in New York, and the history of Orthodoxy in New York … this is a building that raises all these questions and now that building is no more.”

Stein-Milford said while the neighborhood is no longer predominantly Jewish, like it was when the congregation first moved into the building, the destruction is a loss for all New Yorkers.

“The neighborhood is defined by change,” Stein-Milford said. “I was deeply saddened and feel it is a loss for the people who have lived in the neighborhood for years, and the people who will come to live in the neighborhood ... a beautiful historic landmark in the neighborhood is gone and that is a loss.”

Bill Frazer, 58, owns Flowers on Essex and has been in the neighborhood for more than 20 years. Frazer said he smelled the smoke late Sunday night, likening it to “rubber burning.”

“I just thought it was very sad,” he said. “This is a neighborhood that has changed so rapidly, there’s less and less of that Orthodox Jewish presence.

“It’s almost following in the ... footsteps — it’s becoming much more commercialized,” he said about the Lower East Side.

Etzion Neuer, the deputy director of the Anti-Defamation League’s New York Regional Office, said in a statement that the group was in touch with investigators.

“We were heartbroken and disturbed to see the images of a synagogue in flames, even one that has not been in use for several years,” Neuer said. “We are in touch with law enforcement, who are actively investigating the blaze, and we will continue to monitor the situation as it proceeds.”